It might seem like your kids’ bath toys should be ultra clean. After all, they’re getting washed off in the tub with your baby, right? But a new study by Swiss researchers shows that soft plastic bath toys like rubber duckies are breeding grounds for bacteria — some of which can make kids sick.

What the study looked at

It might not come as a surprise that bathrooms are the ideal environment for microbial growth, thanks to high temperatures and humidity. Bathtubs and shower curtains have already been shown to harbor icky bacteria and fungi. And there has even been an outbreak of drug-resistant bacteria in a children’s hospital linked to shared bath toys.

Still, there’s little research on bath toys — which babies and toddlers like to put in their mouths. So researchers wanted to figure out the cleanliness factor of the most classic of all baby bath toys: the rubber ducky.

The study authors collected 19 actual bath toys used under real conditions in randomly chosen houses. They also looked at six new, identical bath toys put in situations meant to simulate the toys’ normal use in clean and dirty bath water. They analyzed samples from the inside of each of the toys to determine how much and what kinds of bacteria and fungi lived there.

What the research found

The study, published in the journal Nature, found that all the toys had “dense and slimy biofilms” (the bacteria and fungi living in the toys) trapped on the inside, and about 70 percent of the real, in-use bath toys had what appeared to be mold growth. Fungi were found on 58 percent of all real and new bath toys, although the most common types of fungi found on the actual bath toys have been previously detected in drinking water systems and in soil.

All the bath toys also had high levels and diverse types of bacteria — on average 75 million cells of bacteria per square centimeter. The most commonly spotted bacteria have been found in drinking water and fresh water systems. Other bacteria are in the human skin, mouth, airways and gastrointestinal tract.

Perhaps the most worrying finding: Eighty percent of the ducks tested positive for at least one “potentially pathogenic bacteria” that can cause eye, ear and stomach infections. That includes legionella, enterococci and Pseudomonas aeruginosa bacteria, all of which are linked to hospital-acquired infections. Chlamydia bacteria were detected on five of the real bath toys.

The authors say that the flexible plastic material used in rubber toys absorbs organic material (like bacteria) from water — which isn’t 100 percent sterile the moment it comes out of the tap. Bath water also contains bodily fluids and additional bacteria and dirt that cling to toys. At the same time, toys leech organic carbon, which feed the bacteria to continue the cycle.

What this means for parents

The authors note that “exposure to bacteria and fungi is not necessarily bad for human health and may indeed even strengthen the immune defense.” And some of the bacteria and fungi found on the toys aren't all that alarming, since they’re commonly found in the tap water we already drink.

That said, however, the study did spot other bugs that can be harmful. That’s especially concerning for kids, who are potentially more vulnerable to infections and are more likely to squeeze water with chunks of biofilm onto their faces and into their mouths.

The authors argue for increased regulations on the types of materials used by manufacturers to make bath toys. Of course, putting these kinds of rules in place takes time, so we may not see them take effect while our little ones are still little.

Always squeeze out all water from toys each time your kids are done bathing. Air-dry and store them in a clean, dry place.

Disinfect bath toys about once a week or so if possible, following manufacturer’s instructions. For the most part, toys can be cleaned in a 1 to 100 bleach solution (about half a cup of bleach per gallon of water), then rinsed off with soap and water.

Try buying bath toys with no holes in them, as they're less likely to accumulate mold and other bacteria.

Above all else, don't panic if your baby puts his rubber ducky in his mouth or your toddler douses herself in water squirted from a bath toy. Just do your best to keep your little ones' bath toys clean, and throw them out if you see any signs of mold.